Air-compressor



(NoModeL) 2 Sheets-Sheet 1..

W. T. PORSTER.

AIR COMPRESSOR.

No. 375,929. Patented Jan. 3, 1888.

N. F ETERS, Phom-Lnhc ra har. Washington, D. C,

(No Model.) ZShets-Sh'eet 2.

W. T. PORSTER.

AIR COMPRESSOR.

No. 375,929. Patented Jan. 3,1888;

W/T/VESSES N, PETERS. Fhalo-Ldhogmplwr. w.1 uuu uuuuuuu c.

UNITED STATES PATENT OFFICE.

\VILLIAM T. FORSTER, OF KANSAS CITY, MISSOURI.

AIR-COMPRESSOR.

SPECIFICATION forming part of Letters Patent No. 375,929, dated January3, 1888.

Application filed October 11, 1885. Renewed February 8, 1887. Serial No.226,968. (No model.)

To all whom it may concern.-

Be it known that 1, WILLIAM T. FORSTER, residingin Kansas City, in thecounty of Jackson and State of Missouri, have invented certain new anduseful Improvements in AlF'GOHI- pressors, of which the following is afull, clear, and exact description, reference being had to theaccompanying drawings, making a partof this specification.

My invention relates to improvements in apparatus for compressing air orother gases; and it consists more particularly in a novel constructionof the valves and mechanism governing the passage of the compressed airfrom the air-cylinder to the receiving vessel or rescrvoir.

In the accompanying drawings, consisting of two sheets, in which likeletters of reference refer to like parts, Figure 1 is a sectionaleleration of my improved compressor, showing one of the cylinder-headsor exhaust-valves pushed out to allow the compressed air to pass fromthe cylinder to the reservoir. Fig. 2 is a plan view of one of the endsof the diaphragm, partly in section, through the line a: or, Fig. 1.Fig. 3 is a viewer" the circular inlet-valve, part of the same beingremoved to show the construction. Fig. 4 is a plan view of the innersurface of one of the cylinderheads or exhaust-valves, the cup E,occupying the center, not being shown.

My improved compressor consists, essentially, of an air-cylindercontaining a piston, in which the air is compressed and which isprovided with movable heads or ends adapt ed to slide outward when theair within has reached the required degree of compression and uncoverthe ports by which the compressed air escapes into the reservoir,'andwhich thus constitute the exhaust -valves of the compressor, and inconnection therewith a dia 'phragm or equalizer consisting of a hollowclosed vessel with flexible ends attached to the outside of the movablecylinder heads and having its interior communicating with the reservoir,so as to be filled with compressed air, and thus exert an outwardpressure on the flexible ends, and thereby on the cylinderheads, equalto the inward pressure of the compressed air in the cylinder. Themovable cylinder-heads are thus made to form balanced valves having anequal balancingprcssure on both their faces or sides just before theyslide outward to uncover the ports, and thus but little extra power inthe piston above that required to compress the airis required to move"or slide the exhaust-valves.

As shown in the drawings, and as I propose to construct my improvedcompressor, A is the air or compression cylinder containing the pistonP, which is moved back and forth by the piston-rod p, in the usualmanner. At each end of the cylinder and fitting closely in the same, soas to inclose the chamber and render it airtight, are the movable headsB and B, provided with the circular inlet-valves O and adapted to slideback and forth in the ends of the cylinder. In the walls of thecylinder, near each end, are circular or other shaped ports (I, whichform the outlets or dischargeorifices, and which communicate with theside or discharge pipe, D, by which the compressed air passes from thecylinder A to the reservoir. The arrangement of the ports and movableheads is such that when the head is in place within the cylinder thesides of the header:- tend over and cover the port, as shown at B, andthus prevent the air from passinginto the discharge-pipe; but when thehead is pushed out, as at B, by the compressed air the head slides pastthe port and uncovers the same, thus allowing the port to communicatewith theinterior of the cylinder and the compressed air to escape intothe discharge-pipe. The movable heads B and B thus form the exhaust-valves of the compressor and control the passage of the compressedair from the cylinder A to the receivingreservoir. As the ports (Z areplaced near the ends of the air-cylinder A, and but a short distancefrom or beyond the inner face or edge of the cylinder heads or valves Band B, when the latter are within the cylinder, the heads are requiredto be moved or slid but a short distancein order to open or uncover theports. The motion of the valves to open and close the outlets or portsis thus very little, insuring prompt action of the valves and decreasingthe friction bolts, as shown in the drawings. The ends or upper andlower slides of the diaphragm L are formed by a circular strip or ring,0, of flexible material-as rubber-secured, by bolts 5 to the outsideedge of the diaphragm or cylinder and by bolts 11 to a rigid centerpiece or disk, N. By reason of this outer circle, 0, of flexiblematerial, the entire extent of the ends or upper and lower sides of thediaphragm are capable of being depressed inward by a press ure fromwithout or forced outward by a pressure from within. A circular frame orring, T and T, is secured, by the bolts n, to the flexible ends on bothsides of the diaphragm, so as to move with the same, and is arranged toslide in recesses m, formed in the frame M.

On the outside of the flexible rings 0, and resting against them, isaseries of steel plates or flat rods, R, (shown more clearly in Fig. 2,)which extend from the edge of the cylinder to the inner edge of the ring0 and completely cover the latter, as is shown in Fig. 2. The outer end,r, of these plates or rods rests loosely in hearings or depressions m inthe frame M, and the inner end, a", rests against the under side of thecircular frames T and T. The plates or rods R are thus held in place andagainst the flexible ring 0 by their extreme ends, and are so arrangedthat the inner end, 1", can freely move back and forth or up and down asthe ends of the cylinder are forced outward or inward.

On the under side of the frames T and T, and at the extreme ends of thelatter, are points or projections 1, which are so constructed andarranged that when the ends of the cylinder, and consequently the framesT and T, have been depressed or moved inward a certain distancetheseprojections will strike or come in contact with the outer surface of theplates or rods B, as is shown in Fig. 1 in the case of the inner orlowerframe, T. \tVhenever the points t come in contact with the plates orrods, they change the fulcrum or movable point of hearing on the latterfrom the inner end, 0", to a point nearer the fixed end 0', and thusdecrease the length of the rod between the points of contact, andthereby increase the resisting power or force of the rods. These platesor rods are preferably made of steel, so as to be capable of resistinggreat pressure, and are constructed of such proportion and theprojections it are so located and arranged that when the latter come incontact with the rods and press them inward the rods exert a resistanceequal to or a little greater than the full press ure of the piston inthe air-cylinder as the latler forces the head or valve outward, andthus the plates or rods, and consequently the ends of the diaphragm,control the movement of the head and prevent its being pushed-out toofar. The circular frame T, and therefore the flexible end of thediaphragm to which it is fastened, is connected by means of the post Swith the outer face or side of the movable cylinder-head or exhaustvalveB in the end of the air-cylinder A, and the opposite frame,

T, and flexible end on the other side of the diaphragm are connected, bymeans of the cross-head X, side rods, 3 y, and cross-heads X X, with themovable cylinder-head or exhaust-valve B in the other end of theair-cylinder. The movable cylinder-heads are thus connected with theflexible ends of the diaphragm and move together with the same. Theinterior of the diaphragm L communic'ates, by' means of the tube a, withthe dis charge-pipe D, and thus with the reservoir containing thecompressed air. The diaphragm is therefore filled or charged withcompressed air at the same degree of compression as. the air in thereceiving-reservoir.

. The diaphragm is constructed of such pro portion with respect to thesize and capacity of the air-cylinder tnat the pressure of the flexibleends of the diaphragm on the movable heads ofthe air-cylinder, or theexhaust-valves B and B, with which they are connected, is equal to thepressure of the compressed air in the reservoir, or. equal to the degreeof compression it is desired to obtain in the air-cylinder A. Thisoutward pressure on the heads or valves B and B holds them in place inthe cylinder and prevents their moving until the air has been compressedto the requi red degree and the valves are required to move.

From the above description and the drawings the operation of thecompressor will be readily understood. The interior of the cyl-- ind erA is filled with air entering through the inlet-valves O in the heads Band B. When the piston commeneesits movement toward either head, theinletwalve O in that head is closed by the pressure of the air in thecylinder and held closely on its seat, thus preventing the escape of theair from the cylinder. As the piston advances toward the head, the airinclosed between the surface of the piston and the inner surface of thehead is compressed until the desired degree of compression is, obtained,or until the air in the cylinder is compressed to the same degree asthat in the reservoir and in the diaphragm communicating with thelatter. At this nioment, as the cylinder and diaphragm both contain airat the same pressure, and as they are constructed of the properproportion with respect to each other, the pressure on the under surfaceof the head or valve, caused by the pressure of the air in front of thepiston, is equal to the pressure on the outer surface of the head orvalve caused by pressure of the air on the flexible end of thediaphragm. The pressure on both sides of the head or valve is thereforethe same, or the valve is balanced between the two equal pressures, andit follows that a very slight additional pressure either way will movethe valve. As the piston continues to advance, the extra or increasedpressure on the underside of thehead or valve forces it outward, and asthe latter moves in the sides of the cylinder it uncovers or slides pastthe ports d, and the compressed air passes or escapes through the sidepipe, D, into the reservoir. As the head or valve slides or movesoutward, it depresses the flexible end of the diaphragm connected withits outer face or surface, as shown in Fig. 1, until the points 15 onthe frame or ringTcome in contact with the plates or rods B, when, asthe rods are so constructed and arranged as to exert a resistancegreater than the pressure of the piston or outward force of the head,the depression ot' the end of the diaphragm, and consequently theoutward movement of the head or valve, is checked, and thus thecylinderhead is prevented from sliding entirely out of the cylinder. Aswill thus be seen, at the moment immediately preceding that at which thehead or valve moves, and when the air in the cylinder has beencompressed to the required degree, the pressure on both surfaces of thehead or valve is equal, the pressure in the cylinder or on the undersurface of the valve balancing that in the diaphragm or on the outersurface of the valve. The force necessary, therefore, to move the valveis only that required to overcome the weight of the valve and thefriction of the latter on the sides of the cylinder. As the valve isheld in place in the cylinder by the pressure of the air in thediaphragm on its outer surface, and not by its own weight, it need notbe very heavy, and as it slides but a little distance in order touncover the ports the force required to move the head or valve is veryslight. In my improved compressor, therefore, the pressure of the pistonnecessary to move the exhaust-valve above that required to compress theair is very slight, and nearly all the power of the piston is applied incompressingthe air. After the compressed air has passed from thecylinder into the reservoir and the piston has commenced itsreturn-stroke to the opposite head the spring or resistance of theplates It, caused by the depression of the flexible end of the diaphragmby the movement of the cylinder-head and the force of the compressed airin the diaphragm, forces this head back in the cylinder to its formerposition, thus closing the ports and preventing the compressed airpassing back into the cylinder.

In order to insure a more perfect movement of the head back into thecylinder and closing of the ports, I employ the device shown at E in thedrawings. This consists of a movable cup, E, fitting in a recess in theinner face or surface of the cylinder heads or valves and adapted toslide outand in in the same. This cup in its normal position projectsjust be yond the face of the head, as shown in the lower part ofFig. 1,being held there by springs c. On the outer surface of the cup is formeda depression or cavity, F, from which extend small channels f throughthe head,terminatin g in the outer face or surface of the latter. Inthese channels and connected with the cup are valves h, so arranged thatwhen the cup is in its normal position, projecting beyond the surface ofthe head, these valves are closed. After the piston has forced the heador exhaust-valve outward and opened the ports, it continues to advanceas the air passes from the cylinder until all the air has escaped fromthe cylinder and the piston has come in contact with the head. As thecup E projects be yond the surface of the head, the piston first strikesit and incloses or shuts in theair contained in the depression or cavityF. The piston, continuing to advance, forces the cup back,and at thesame time opens the valves it, connected with it, as shown at E, and theair contained in the depression escapes through the ehannelsf out of thecylinder. It follows, therefore,that when the piston has reached thehead and is ready to return, the pressure of the air on thelower orinnersurface of the head is reduced by the amount ofair which has escapedfrom the depression in the cup E. The pressure on the inner surface ofthe head is thus less than that on the outer surface,caused by the airin the diaphragm. The cylinderhead is therefore pressed down and heldclosely against the surface of the piston by the greater pressure in thediaphragm, and as the piston returns the head slides back with it; hencethe movement of the head back into the cylinder is a very quick one,andthe ports are immediately closed, and,moreover,as the head is held downclose against the piston, there is no opportunity for the compressed airto pass back into the cylinder. The cup or device E, furthern1ore,actsas a cushion for the piston to strike against, and prevents the pistonand cylinder-head from being injured when they come in contact with eachother.

Any variety of inlet-valves may be used to admit the air into thecylinder; but I prefer to employ the valves shown in the drawings at C.These valves (shown more at large in Fig. 3) are circular and work in avalve-seat on the inner surface of the cylinder-head. The valves consistof the V-shaped body 0, made of iron or other suitable metal,to which isseeured,by means of the bolts 7c, the face-plate K. Between the body 0and plate K is placed a tub ber ring or cushion, I. The valve is held inthe valve-seat by the stems G, arranged to allow the valve to play upand down in the seat, and provided with the spring 9, to force the valvein when the pressure of the air in the cylinder against the face orplateK is removed. As the valve is forced in or opened by means of thespring 9, the air, entering through the passage 0, passes between thevalves and valveseat and enters the cylinder. As the piston moves towardthe head of the cylinder and compresses the air within, it forces thevalve against the valveseat and closes the valve, thus preventing thepassage of the air between the valve and seat. By means of the rubbercushion or packing I, as the valve is pressed against its seat, a moreperfect and effective air-tight joint is insured, and at the same timethe blow or impact of the valve is lessened.

To insure a tightjointbetween the cylinder heads or valves and the sidesof the cylinder,

IIO

IIS

rubber bands or packing are arranged in the sides of the valves, whichis pressed closely against the sides of the cylinder by the compressedair introduced through the tubes V, communicating with the side pipe, D.

In my improved compressor I require very little extra force or power tomove the valves, and as the valves slide but a little distance they aresubject to but little wear, and do not require to be frequentlyrefitted, as is the case with the valves now in use; and, moreover, asthe valves are held in place by the force of the compressed air in thediaphragm, which is the same as in the reservoir, the valves ad- 1 justthemselves to any pressure required, al-

ways moving when the air in the cylinder is compressed to the degreedesired or to the same degree as that in the reservoir. By a suitablearrangement of the plates R and projections t the diaphragm can be madeto resist any degree of pressure required. This construction ofdiaphragm may also be used as a buffer wherever it is necessary toresist or overcome pressure.

What I claim as new is- 1. In an air-compressor, an exhaust-valveconnected with a flexible diaphragm communicating with the reservoir ofcompressed air and containing air at the same degree of press me as isproduced in the cylinder, so as to be held in place by the pressure inthe dia phragm and thus balanced between the two pressures,substantially as and for the purposes set forth.

2. In an air-compressor, the combination, with the air-cylinder providedwith movable heads, of a diaphragm or equalizer having flexibleendsconnected with the movable the diaphragm L, communicating by a pipewith the reservoir of compressed air in order to contain air at the samedegree of pressure as is produced in the air-cylinder and havingflexible ends connected with the cylinderheads B B, substantially as andfor the purposes set fortht at. In an aincompressor, the combination ofthe aircylinder A, having the ports (I at or near each end and providedwith the movable heads B B, having the valves 0, and cups E, with thediaphragn'i L, communicating with the reservoir of compressed air, so asto contain air at the same degree of pressure as is produced in theair-cylinder, and provided with the flexible rings 0, disks N N, elasticplates R, and frames TT, connecting with the movable cylinder-heads B Band having projection's t, for acting upon the elastic plates R,arranged and operating substantially as described,and for the purposesset forth.

5. In an air-compressor, the diaphragm or equalizer It, capable ofcontaining compressed air, consisting of the hollow body L, having thecentral disks, N N, the flexible rings 0, attached to and connectingsuch disks with the sides of the diaphragm, the elastic plates R,arranged on the rings 0, and the frames 'I T, secured to the disks N Nand provided with projections i, adapted to act on the plates It,substantially as and for the purposes set forth.

6. In an aincompressor, the combination, with the cylinder-heads B B, ofthe movable cups E, fitting and moving in suitable recesses in suchheads, constructed with or having a cavity or air space, F, and providedwith channels or discharge orifices f and valves to close the same, asand for the purpose set.

forth.

Dated this 28th day of September, 1885.

'WILLI AM T. FORSTER.

Vitnesses:

JULIET M. FORSTER, FRANCIS L. Gnoss.

